Subscriber unit for managing dual wireless communication links

ABSTRACT

A technique for communication with a local area network (LAN) via a wireless connection determines whether a first short-range, high-speed, wireless communication path is available and connects to the LAN using a longer range, lower speed wireless communication path if the short-range, high-speed wireless communication path is not available. The low-range, high-speed wireless communication path is a wireless communication path is a wireless LAN connection such as an IEE 802.11-compliant wireless LAN and the long-range, low-sped wireless communication mode is a cellular CDMA-type connection. Determining whether the first IEEE 802.11 mode is available can be done by detecting a beacon signal, or transmitting a probe request message and detecting a probe response message in response to the probe request, indicating the presence or availability of the short-range, high-speed wireless communication path. Alternatively, the availability of short-range, high-speed wireless communication path can be detected by simply detecting activity on it.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/753,149 filed Jan. 29, 2013; which is a continuation of U.S.application Ser. No. 12/615,098 filed Nov. 9, 2009; now U.S. Pat. No.8,380,244 issued Feb. 19, 2013, which is a continuation of U.S.application Ser. No. 11/326,809 filed Jan. 6, 2006, now U.S. Pat. No.7,616,970 issued Nov. 10, 2009. U.S. application Ser. No. 11/326,809,now U.S. Pat. No. 7,616,970 issued Nov. 10, 2009 is a continuation ofU.S. application Ser. No. 10/358,082 filed Feb. 3, 2003, now U.S. Pat.No. 7,013,162 issued Mar. 14, 2006 and a continuation of U.S.application Ser. No. 10/341,528 filed Jan. 13, 2003, now U.S. Pat. No.7,024,222 issued Apr. 4, 2006. U.S. application Ser. No. 10/358,082filed Feb. 3, 2003, now U.S. Pat. No. 7,013,162 issued Mar. 14, 2006 andU.S. application Ser. No. 10/341,528 filed Jan. 13, 2003, now U.S. Pat.No. 7,024,222 issued Apr. 4, 2006, are both continuations of U.S.application Ser. No. 09/400,136 filed Sep. 21, 1999, now U.S. Pat. No.6,526,034 issued Feb. 25, 2003. The entire teachings of the aboveapplications are incorporated by reference herein.

BACKGROUND OF THE INVENTION

The widespread availability of personal computers at low cost has led toa situation where the general public increasingly demands access to theInternet and other computer networks. A similar demand exists forwireless communications in that the public increasingly demands thatcellular telephones be available at low cost with ubiquitous coverage.

As a result of its familiarity with these two technologies, the generalpopulation now increasingly wishes to not only access computer networks,but to access such networks in wireless fashion as well. This is ofparticularly concern to users of portable computers, laptop computers,hand-held personal digital assistants (PDAs) and the like, who wouldprefer and indeed now expect to be able to access such networks with thesame convenience they have grown accustomed to when using their cellulartelephones.

Unfortunately, there still is no widely available satisfactory solutionfor providing low cost, broad geographical coverage, high speed accessto the Internet and other networks using the existing wirelessinfrastructure which has been built at some expense to support cellulartelephony. Indeed, at the present time, the users of wireless modemsthat operate with the existing cellular telephone network oftenexperience a difficult time when trying to, for example, access theInternet to view web pages. The same frustration level is felt in anysituation when attempting to perform other tasks that require thetransfer of relatively large amounts of data between computers.

This is at least in part due to the architecture of cellular telephonenetworks, which were originally designed to support voicecommunications, as compared to the communications protocols in use forthe Internet, which were originally optimized for wirelinecommunication. In particular, the protocols used for connectingcomputers over wireline networks do not lend themselves well toefficient transmission over standard wireless connections.

For example, cellular networks were originally designed to deliver voicegrade services, having an information bandwidth of approximately threekilohertz (kHz). While techniques exist for communicating data over suchradio channels at the rate of 9600 kilobits per second (kbps), such lowfrequency channels do not lend themselves directly to transmitting dataat rates of 28.8 kbps or even the 56.6 kbps that is now commonlyavailable using inexpensive wireline modems. These rates are presentlythought to be the minimum acceptable data rates for Internet access.

This situation is true for advanced digital wireless communicationprotocols as well, such as Code Division Multiple Access (CDMA). Eventhough such systems convert input voice information to digital signals,they too were designed to provide communication channels at voice gradebandwidth. As a result, they use communication channels that may exhibita bit error rate (BER) as high as one in one thousand bits in multipathfading environments. While such a bit error rate is perfectly acceptablefor the transmission or voice signals, it becomes cumbersome for mostdata transmission environments.

Unfortunately, in wireless environments, access to channels by multiplesubscribers is expensive and there is competition for them. Whether themultiple access is provided by the traditional Frequency DivisionMultiple Access (FDMA) using analog modulation on a group of radiocarriers, or by newer digital modulation schemes that sharing of a radiocarrier using Time Division Multiple Access (TDMA) or Code DivisionMultiple Access (CDMA), the nature of the cellular radio spectrum issuch that it is a medium that is expected to be shared. This is quitedissimilar to the traditional environment for data transmission, inwhich the wireline medium is relatively inexpensive to obtain, and istherefore not typically intended to be shared.

On the other hand, wireless local area networks (W-LANs) have beendeveloped to allow communications between users over a relatively smallrange without the need for a physical connection, or alternatively, toallow communications between a wired LAN and wireless users. W-LANstypically have a much smaller range and higher data rates.

A newly accepted standard, IEEE 802.11, specifies a protocol for themedia access control (MAC) and physical (PHY) layers of a wireless LAN.As with cellular systems, a W-LAN connection can be handed off from onearea of coverage (a “basic service set” in IEEE 802.11 parlance) to thenext. A good description of wireless LANs, and the IEEE 802.11 standardin particular, may be found in Geier, J., Wireless LANs (MacmillanTechnical Publishing, 1999).

SUMMARY OF THE INVENTION

Wireless LANs are generally private networks, that is they areinstalled, owned, and maintained by a private party, such as a business,educational institution or home owner. Such networks are thereforegenerally cheaper to access than long range networks which utilizeshared public access frequencies licensed by a government authority tocomplete a connection, and which generally require subscriber fees.

In addition, W-LANs typically operate at a much faster data rate thanthe long range network. However, as the word “local” implies, the rangeof a W-LAN is rather limited—typically tens or hundreds of feet, ascompared to several miles for a long range cellular telephone network.

It would therefore be desirable to have a device which can automaticallyselect the cheaper and faster W-LAN when possible, e.g., when within itsrange, and to resort to the long range cellular network when access tothe W-LAN is not possible or practical. Previously, two devices wouldhave been required, one for accessing the WLAN and one for accessing thelong range network. At best, these two devices could fit into two slotsin, for example, a laptop computer, requiring the user to select, eitherthrough software or hardware, which device, and hence, which network toaccess. The user might typically then have to disconnect one of thedevices to install the other, and manually reconfigure the computer.

The present invention, on the other hand, is a single device whichconnects directly to a W-LAN using a protocol such as IEEE 802.11 whensuch a connection is possible, and automatically reverts to connectingto the long range network only when out of range of the W-LAN basestations.

Thus, the same equipment can be used without any reconfiguration andeven without the knowledge of the user. For example, when the user is ona company campus and within range of the less expensive, faster W-LAN,the user's laptop or PDA automatically communicates with the W-LAN. Ifthe user leaves the office, for example, for lunch, or at the end of theday, heads home, the same laptop or PDA, being out of range of theW-LAN, will automatically communicate instead with the wider range, moreexpensive cellular network.

Therefore, the present invention is also a method which uses a firstwireless digital communication path and a second wireless digitalcommunication path for coupling data communication signals with a localwireless transceiver at a first site. The second digital communicationpath provides wider coverage and a slower communication rate than thefirst digital communication path. The local wireless transceiverconducts wireless communications with a remote wireless transceiver at asecond site.

One of the wireless communication path is selected upon a request toestablish a communication session between the first and second sites byfirst determining whether the first wireless digital communication pathis available.

In one embodiment, the first wireless communication path comprises awireless LAN connection, preferably using carrier sense multiple accesswith collision avoidance (CSWCA), preferably according to the IEEE802.11 specification. The second wireless communication path comprises acellular connection. Access costs associated with the first wirelesscommunication path are smaller than access costs associated with thesecond wireless communication path. Preferably, access to the firstwireless communication path is essentially free, excluding expenses suchas set-up and maintenance costs, while access to the second wirelesscommunication path can be subscription-based.

The local wireless transceiver can be a single transceiver which iscapable of communicating with a second site or destination over bothwireless communication paths. Alternatively, the local wirelesstransceiver can comprise two transceivers, one for each communicationpath.

In one embodiment, the first wireless communication path is a privatenetwork. Conversely, the second wireless communication path can be apublic network, in which channels are allocated centrally.

In one embodiment, the step of determining whether the first wirelesscommunication mode is available is performed by passive scanning, suchas by detecting a beacon signal. In another embodiment, active scanningis used, for example, by transmitting a probe request message anddetecting a probe response message in response to the probe requestwhich indicates the presence of the first wireless communication path.In yet another embodiment, determining whether the first wirelesscommunication path is available comprises simply detecting activity onthe first wireless communication path.

If the first wireless digital communication mode is available, acommunication session between the first and second sites using the firstwireless digital communication path is established.

On the other hand, if the first wireless digital communication path isnot available, a communication session between the first and secondsites using the second wireless digital communication path isestablished. In this case, the local wireless transceiver is controlledto make it appear to the second wireless digital communication path asthough the bandwidth were continuously available during thecommunication session, irrespective of any actual need to transport datacommunication signals between said first and second sites. In theabsence of such a need to transport data communication signals betweenthe first and second sites, the bandwidth is made available for wirelesscommunication by other wireless transceivers.

In one preferred embodiment, the second wireless digital communicationpath is provided by establishing a logical connection using a higherlayer protocol, such as a network layer protocol, from a subscriberunit, such as may be connected to a portable computer node, to anintended peer node, such as another computer. The network layer logicalconnection is made through a wireless channel which provides a physicallayer connection between the portable computer node, through a basestation, and the intended peer node. In response to relatively lowutilization of the wireless channel, the physical layer channel isreleased while maintaining the appearance of a network layer connectionto the higher level protocols.

This has two consequences. First, it frees wireless channel bandwidthfor use by other subscriber units, without the overhead associated withhaving to set up an end to end connection each time that data needs tobe transferred. In addition, and perhaps more importantly, by allocatingwireless channels only when needed, the bandwidth necessary to provide atemporary but very high speed connection is available at critical times.These may occur, for example, when a particular subscriber unit requeststhat a web page file be downloaded from the Internet.

More specifically, the technique, which is here called spoofing,involves stripping off the lower layers of the protocol whilereformatting higher layer messages for transmission using a moreefficient CDMA based encapsulated protocol.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is a block diagram of a system in which a portable device such asa laptop computer making use of a protocol converter according to theinvention to connect to a computer network over a wireless cellularlink.

FIG. 2 is a diagram depicting how network layer data frames are dividedamong multiple physical links or channels.

FIG. 3 is a more detailed diagram showing how network layer frames aredivided into subframes by a protocol converter located at a sender.

FIG. 4 is a continuation of the diagram of FIG. 3.

FIG. 5 is a schematic diagram of a short range, high speed wireless LANoverlapping with a longer range, lower speed wireless communicationnetwork.

FIG. 6 is a high-level block diagram of a subscriber unit of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Turning attention now to the drawings more particularly, FIG. 1 is ablock diagram of a system 10 for implementing high speed datacommunication over a cellular link according to the invention. Thesystem 10 consists of a remote or subscriber unit 20, multiplebi-directional communication links 30, and a local or service providerunit 40.

The subscriber unit 20 connects to terminal equipment 22 such as aportable or laptop computer, hand held Personal Digital Assistant (PDA)or the like, via a computer interface 24 such as a modem. The interface24 in turn provides data to a protocol converter 25, which in turnprovides data to a multichannel digital transceiver 26 and antenna 27.

The interface 24 receives data from the computer 20, and together withappropriate hardware and/or software, converts it to a format suitablefor transmission such as in accordance with known communicationstandards. For example, the interface 24 may convert data signals fromthe terminal equipment 22 to a wireline physical layer protocol formatsuch as specified by the Integrated Services Digital Network (ISDN)standard at rates of 128 kbps, or the Kflex standard at rates of 56.6kbps. At a network layer, the data provided by the interface 24 ispreferably formatted in a manner consistent with suitable networkcommunication protocols such as TCP/IP to permit the terminal equipment22 to connect to other computers over networks such as the Internet.This description of the interface 24 and protocols is exemplary only andit should be understood that other protocols can be used.

The protocol converter 25 implements an intermediate protocol layersuitable for converting the data provided by the interface 24 to aformat appropriate for the multichannel transceiver 26 according to theinvention, and as is described in greater detail below.

The multichannel digital transceiver 26 provides access to one or morephysical communication links such as the illustrated radio channels 30.The physical links are preferably known wireless communication airinterfaces using digital modulation techniques such as Code DivisionMultiple Access (CDMA) standard specified by IS-95. It should beunderstood that other wireless communication protocols and other typesof links 30 may also be used to advantage with the invention.

The channels 30 represent one or more relatively slower communicationchannels, such as operating at a 9.6 kbps rate typical of voice gradecommunication. These communications channels may be provided by a singlewide bandwidth CDMA carrier such as having a 1.25 MegaHertz bandwidth,and then providing the individual channels with unique orthogonal CDMAcodes. Alternatively, the multiple channels 30 may be provided by singlechannel communication media such as provided by other wirelesscommunication protocols. However, what is important is that the neteffect multiple channels 30 represent multiple communication channelsthat may be adversely effected by significant bit error rates that areunique to each link 30.

An “error” as described herein is a bit error perceived at the higherlayer such as the network layer. The invention only strives to improvethe system level bit error rate, and does not attempt to guaranteeabsolute data integrity.

On the local provider unit, the service provider equipment 40 may forexample be implemented at a wireless Internet Service Provider (ISP)40-1. In this case, the equipment includes an antenna 42-1, amultichannel transceiver 44-1, a protocol converter 46-1, and otherequipment 48-1 such as modems, interfaces, routers, and the like whichare needed for the ISP to provide connections to the Internet 49-1.

At the ISP 40-1, the multichannel transceiver 44-1 provides functionsanalogous to the multichannel transceiver 26 of the subscriber unit, butin an inverse fashion. The same is true of the protocol converter 46-1,that is, it provides inverse functionality to the protocol converter 25in the subscriber unit 20. The ISP 40-1 accepts data from the protocolconverter 46-1 in the TCP/IP frame format and then communicates suchdata to the Internet 49-1. It should be understood that theconfiguration of the remaining ISP equipment 48-1 may take any number offorms such as a local area networks, multiple dial up connections, T1carrier connection equipment, or other high speed communication links tothe Internet 49-1.

Alternatively, the provider 40 may function as a radio base station in acellular telephone system to permit a dial-up connection between theterminal equipment 22 and a server 49-2. In this instance, the basestation 40-2 includes an antenna 42-2, multichannel transceiver 44-2,and protocol converter 46-2 providing one or more connections to apublic switched telephone network (PSTN) 48-2, and ultimately to theserver 49-2.

In addition to the illustrated implementations 40-1, 40-2, there may bevarious other ways of implementing the provider 40 in order to provide aconnection to data processing equipment from the terminal equipment 22.

Attention is now turned to the functions of the protocol converters 25and 46, which can be thought of as an intermediate layer within thecontext of the Open System Interconnect (OSI) model for communication.In particular, the protocol converter provides a bandwidth managementfunctionality 29 implemented between a physical layer such as thatprovided by the CDMA protocol in use with the multichannel transceivers26 and a network layer protocol such as TCP/IP providing connectionsbetween the terminal equipment 22 and the Internet 49-1 or server 49-2.

The bandwidth management functionality 29 preferably provides a numberof functions in order to keep both the physical layer and network layerconnections properly maintained over multiple communication links 30.For example, certain physical layer connections may expect to receive acontinuous stream of synchronous data bits regardless of whetherterminal equipment at either end actually has data to transmit. Suchfunctions may also include rate adaption, bonding of multiple channelson the links, spoofing, radio channel setup and takedown.

The present invention is more particularly concerned with the techniqueused by the protocol converters 25 and 46 for adjusting the frame sizeof individual channels used over each of the multiple links 30 in orderto improve the effective throughput rate between a sender and a receiverin a bit error rate prone environment. It should be understood in thefollowing discussion that the connections discussed herein arebidirectional, and that a sender may either be the subscriber unit 22 orthe provider unit 40.

More specifically, the problem addressed by the present invention isshown in FIG. 2. The frame 60 as received at the receiver end must beidentical to the frame 50 originating at the sender. This is despite thefact that multiple channels are used with much higher bit error rates,with the received frame 60 being transmitted reliably with a bit errorrate of 10⁻⁶ or better as is typically required in TCP/IP or othernetwork layer protocols. The present invention optimizes the effectivedata throughput such that the received frames 60 are not affected by theexperienced bit error rate performance of network layer connections.

It should be understood that another assumption is that the individualchannels 30-1, 30-2 . . . 30-N may experience different bit error ratelevels both over time and in an average sense. Although each of thechannels 30 may operate quite similarly, given the statistical nature oferrors, identical behavior of all of the channels 30 is not assumed. Forexample, a specific channel 30-3 may receive severe interference fromanother connection in a neighboring cell, and be capable of providingonly a 10⁻³ bit error rate whereby other channels 30 may experience verylittle interference.

In order to optimize the throughput for the system 10 on a global basis,the invention also preferably optimizes the parameters of each channel30 separately. Otherwise, a relatively good channel 30-1 might sufferdown speed procedures required to accommodate a weaker channel 30-3.

It should also be understood that the number of channels 30 that may beneeded to carry a single data stream such as a rate of 128 kbps at agiven point in time may be relatively large. For example, up to 20channels 30 may be assigned at a particular time in order to accommodatea desired data transfer rate. Therefore, the probability ofsignificantly different characteristics in any given one of the channels30 is high.

Turning attention now more particularly to FIG. 3, the operations of theprotocol converter 25 or 46 at the sender will be more particularlydescribed. As shown, the input frame 50 as received from the networklayer is relatively large, such as for example 1480 bits long, in thecase of a TCP/IP frame.

The input frame 50 is first divided into a set of smaller pieces 54-1,54-2. The size of the individual pieces 54 are chosen based upon theoptimum subframe size for each of the channels 30 available. For examplea bandwidth management function may make only a certain number ofchannels 30 available at any time. A subset of the available channels 30is selected, and then the optimum number of bits for each subframeintended to be transmitted over respective one of the channels, is thenchosen.

Thus, as illustrated in the figure, a given frame 54-1 may be dividedinto pieces associated with four channels. At a later time, there may benine channels 30 available for a frame, with different optimum subframesizes for the piece 54-2.

Each of the subframes 56 consists of a position identifier 58 a, a dataportion 58 b, and a trailer typically in the form of an integritychecksum such as a cyclic redundancy check (CRC) 58 c. The positionidentifier 58 a for each subframe indicates the position within theassociated larger frame 50.

The subframes 56 are then further prepared for transmission on eachchannel 30. This may be done by adding a sequence number related to eachchannel at the beginning of each subframe 56. The subframe 56 is thentransmitted over the associated channel 30.

FIG. 4 illustrates the operations performed at the receive side. Thesubframes 56 are first received on the individual channels 30. Asubframe 56 is discarded as received if the CRC portion 58 c is notcorrect.

The sequence numbers 58 d of the remaining frames 56 are then strippedoff and used to determine whether any subframes 56 are missing. Missingsubframes 56 can be detected by comparing the received sequence numbers58 d. If a sequence number is missing, it is assumed that the associatedsubframe 56 was not received properly. It should be understood thatappropriate buffering of data and subframes 56 is typically required inorder to properly receive the subframes 56 and determine if there areany missing sequence numbers depending upon the transmission rates,number of channels 30 and propagation delays in effect.

Upon the detection of a missing subframe 56, retransmission of themissed subframe is requested by the receiving end. At this point, thetransmitting end reperforms transmission of the missing subframe.

Once all of the subframes 56 are received, the position number 58 a isused to arrange the data from the subframes 56 in the proper order toconstruct the output received frame 60.

At this point, also, if any piece of the large output frame 60 is stillmissing, such as when an end of frame command is encountered,retransmission of the corresponding subframe can also be requested atthe indicated position, specifying a length for the missing piece.

Because of the use of both the position and sequence numbers, the senderand receiver know the ratio of the number of subframes received witherrors to the number of frames received without errors. Also, thereceiver and sender know the average subframe length for each channel.The optimum subframe size can thus be determined for each channel fromthese parameters as is described more fully in U.S. Pat. No. 6,236,647filed on Feb. 24, 1998, entitled “Dynamic Frame Size Adjustment andSelective Reject On a Multi-Link Channel to Improve Effective Throughputand Bit Error Rate,” incorporated herein by reference in its entirety,and assigned to Tantivy Communications Corp., the assignee of thepresent application.

FIG. 5 illustrates a short range, high speed wireless LAN (W-LAN)overlapping with a longer range, lower speed wireless cellularcommunication network (“long range network”). Specifically, within thelonger range, lower speed system, which may be a digital cellular mobiletelephone system, there are multiple long range regions or “cells” 601and 603 which provide coverage throughout a given physical area. Therange or coverage for each cell 601, 603 is on the order of, forexample, greater than one mile radius.

A cellular base station 605 transmits and receives data through itsantenna 171 to mobile units located within its associated cell 601. Thebase station 605 is connected to a public network 619 such as the publicswitched telephone network (PSTN) or preferably a point of presence(POP) or other data connection 621 to the Internet.

Shown within the cell 601 associated with base station 605 is a wirelesslocal area network (W-LAN) 607. Several terminals or computers 609 areconnected directly to the W-LAN 607, including a gateway 609A which isalso connected to the public network 619 via any well-known means 621.In addition, two wireless LAN hubs 611A, 611B are connected to the LAN607. Each wireless LAN hub 611 has a region of coverage 613A, 613B; thecoverage area of the two hubs 611A, 611B may overlap as shown in FIG. 5.The regions of coverage 613A, 613B are generally of the order of tens orhundreds of feet, which is significantly smaller than the cells 601, 603associated with the long range network. In this respect, it isparticularly important to note that FIG. 5 is not drawn to scale.

Also shown are two subscriber units or terminals, such as portablecomputers, employing the present invention. The first terminal 615 iswithin range 613A of a wireless LAN base station 611, while the secondterminal 617 is outside the range of either wireless LAN base station611A, 611B but within the range 601 of the long range network basestation 605.

Because communication within the short range wireless LAN 613A or 613Bis faster and less expensive as compared to the long range network, itis desirable to communicate using the short range path, i.e., the W-LANprotocol, rather than the more costly long range network, when a user'scomputer terminal 615 is within range of a WLAN base station 611, i.e.,within the region of coverage 613A, 613B.

On the other hand, it is desirable that a terminal such as terminal 617,which is not within range of a wireless LAN base station 611,automatically communicate through the long range network's base station605. Thus it is a primary feature of the present invention that aterminal such as 615 or 617 detects the presence or availability of awireless LAN hub 611A or 611B, such as an IEEE 802.11-compliant W-LANhub. This can be done in several ways. For example, IEEE 802.11specifies that a beacon frame should be transmitted at regularintervals. A terminal 615, 617 can detect the beacon frame by waiting aminimum period of time equal to the beacon interval. See, for example,Geier, J., Wireless LANs, pages 137 and 149, (Macmillan TechnicalPublishing, 1999), incorporated herein by reference, which describes howa W-LAN beacon signal is formatted.

Alternatively, a terminal such as 615 may actively transmit a proberequest frame. A wireless LAN base station 611 receiving such a proberequest frame will respond with a probe response frame. Receipt of theprobe response frame by the terminal 615 indicates accessibility of thewireless LAN, and the terminal 615 will use the wireless LAN and bypassthe long range network.

If, on the other hand, no beacon is received within the specified timeperiod or no probe response frame is returned from the base frame, aswould be the case with terminal 617, the terminal assumes that thewireless LAN base stations 611 are not accessible and insteadcommunicates with the long range base station 605 using the long rangenetwork protocol rather than IEEE 802.11 protocol.

Yet another alternative is simply to listen for activity on the wirelessLAN 611. If no activity is heard, the terminal 615, 617 assumes that theLAN is not accessible, and uses the long range communication system.

FIG. 6 shows a terminal 615 which includes a subscriber unit 101incorporating the features of the present invention. A user at thisterminal 615 desires to communicate with a second site using a portablecomputer 110, PDA or other similar device. The computer 110 is connectedto the subscriber unit 101. For example, the subscriber unit 101 may bea PCMCIA card which plugs into a PCMCIA slot, or it may connect to thecomputer 110 with a modem cable.

The subscriber unit 101 itself preferably consists of an interface 120,a CDMA protocol converter 130 that performs various functions includingspoofing 132 and bandwidth management 134 as described earlier, a CDMAtransceiver 140, a W-LAN protocol converter 230, a W-LAN transceiver240, a W-LAN detection circuit 201, path selection switches 211A, 211B,and a subscriber unit antenna 150. The various components of thesubscriber unit 101 may be realized in discrete devices or as anintegrated unit. For example, an existing conventional computerinterface 120 such as the PCMCIA, ISA bus, PC1 bus, or any othercomputer interface may be used together with existing transceivers 140,240. In this case, the unique functions are provided entirely by theprotocol converters 130, 230 which may be sold as separate devices, theW-LAN detection circuit 201 and the mode selection switches 211A, 211B.

Alternatively, the interface 120, protocol converters 130, 233, andtransceivers 140, 240 may be integrated as a complete unit and sold as asingle subscriber unit device 101. Other types of interface connectionssuch as Ethernet, ISDN, or still other data connections may be used toconnect the computing device 110 to the protocol converter 130.

The CDMA protocol converter 130 performs spoofing 132 and basicbandwidth management 134 functions. In general, spoofing 132 consists ofinsuring that the subscriber unit 101 appears, to the terminal equipment110, to be connected to the public network 619 (FIG. 5) on the otherside of the base station 605 at all times.

The bandwidth management function 134 is responsible for allocating anddeallocating CDMA radio channels 160 as required. Bandwidth management134 also includes the dynamic management of the bandwidth allocated to agiven session by dynamically assigning sub-portions of the CDMA radiochannels 160 in a manner using a protocol such as that describedpreviously.

The CDMA transceiver 140 accepts the data from the protocol converter130 and reformats this data in appropriate form for transmission throughthe subscriber unit antenna 150 over the radio link 160. The CDMAtransceiver 140 may operate over only a single 1.25 MHz radio frequencychannel or, alternatively, may be tunable over multiple allocatableradio frequency channels.

CDMA signal transmissions are then received and processed by the basestation equipment 605 (FIG. 5). The base station 605 then couples thedemodulated radio signals to, for example, the public network 619 in amanner which is well known in the art. For example, the base station 605may communicate with the public network 619 over any number of differentefficient communication protocols such as primary rate, ISDN, or otherLAPD based protocols such as IS-634 or V5.2.

It should also be understood that data signals travel bidirectionallyacross the CDMA radio channels 160. In other words, data signalsreceived from the public network 619 are coupled to the portablecomputer 110 in a forward link direction, and data signals originatingat the portable computer 110 are coupled to the public network 619 in aso-called reverse link direction.

Continuing to refer to FIG. 6 briefly, in the long range, lower datarate mode, the spoofing function 132 involves having the CDMAtransceiver 140 loop back synchronous data bits to spoof the terminalequipment 110 into believing that a sufficiently wide wirelesscommunication link 160 is continuously available. However, wirelessbandwidth is allocated only when there is actual data present from theterminal equipment to the CDMA transceiver 140. Therefore, the networklayer need not allocate the assigned wireless bandwidth for the entiretyof the communications session.

That is, when data is not being presented upon the terminal equipment tothe network equipment, the bandwidth management function 134 deallocatesinitially assigned radio channel bandwidth 160 and makes it availablefor another transceiver and another subscriber unit 101.

W-LAN detection circuit 201 detects the presence or availability of aW-LAN base station 611 using, for example, one of the techniquespreviously discussed. If no W-LAN base station is detected, switches211A and 211B are controlled by the detection circuit 201 such that theCDMA protocol converter 130 is switched in along with the CDMAtransceiver 140.

If, on the other hand, a W-LAN is detected, switches 211A and 211B areswitched to the position shown to utilize the W-LAN protocol converter230 and transceiver 240, which are preferably IEEE 802.11-compliant.Note that the path switches 211A; 211B may be implemented in software orhardware, or a combination of hardware and software. Other functions mayalso be implemented in hardware and/or software which may further beshared by the W-LAN and CDMA sections where appropriate.

Furthermore, the long-range, low-speed CDMA path could be selected afterfailure to communicate over the short-range, high speed path for anyreason, for example, the inability to successfully complete acommunication after some predetermined time period.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A subscriber unit comprising: a first transceiver configured tocommunicate with a first wireless network via a plurality of assignedphysical layer channels; a second transceiver configured to communicatewith a second wireless network; and a processor coupled to the firsttransceiver and the second transceiver, and configured to maintain acommunication session, above a physical layer, with the first wirelessnetwork in the absence of the plurality of assigned physical layerchannels.
 2. The subscriber unit of claim 1, wherein the first wirelessnetwork is a cellular wireless network and the second wireless networkis an IEEE 802.11 compliant wireless network.
 3. The subscriber unit ofclaim 2, wherein the second wireless network is an IEEE 802.11xcompliant wireless network.
 4. The subscriber unit of claim 1, whereinthe second transceiver is configured to transmit transmission controlprotocol and Internet protocol (TCP/IP) data to the second wirelessnetwork while the communication session above the physical layer ismaintained.
 5. The subscriber unit of claim 1, wherein the communicationsession above the physical layer is a transmission control protocol(TCP) layer session, an Internet protocol (IP) layer session, or anetwork layer session.
 6. The subscriber unit of claim 2, furthercomprising: a detector configured to detect the IEEE 802 compliantwireless network; and a circuit configured to select the secondtransceiver in response to the detector detecting the IEEE 802 compliantwireless network.
 7. The subscriber unit of claim 6, wherein theprocessor is further configured to release the plurality of assignedphysical layer channels.
 8. The subscriber unit of claim 6, wherein thedetector is configured to detect a beacon frame or a probe responseframe received by the second transceiver from the IEEE 802 compliantwireless network.
 9. The subscriber unit of claim 1, wherein at leastone of the plurality of physical layer channels is a data channel. 10.The subscriber unit of claim 2, wherein the first wireless network is acode division multiple access (CDMA) wireless network and the secondwireless network is an IEEE 802.11x compliant wireless network, and thefirst transceiver is a cellular code division multiple access (CDMA)transceiver and the second transceiver is an IEEE 802.11x complianttransceiver.
 11. A method for use in a dual mode subscriber unit, themethod comprising: establishing a non-physical layer communicationsession with a first wireless network; maintaining the non-physicallayer communication session in the absence of any physical layerchannels associated with the first wireless network; and communicatingwith a second wireless network while maintaining the non-physical layercommunication session with the first wireless network.
 12. The method ofclaim 11, wherein the first wireless network is a cellular wirelessnetwork and the second wireless network is an IEEE 802 compliantwireless network.
 13. The method of claim 12, wherein the secondwireless network is an IEEE 802.11x compliant wireless network.
 14. Themethod of claim 11, wherein communicating with the second wirelessnetwork comprises transmitting transmission control protocol andInternet protocol (TCP/IP) data.
 15. The method of claim 11, wherein thenon-physical layer communication session is a transmission controlprotocol (TCP) layer session, an Internet protocol (IP) layer session,or a network layer session.
 16. The method of claim 12, furthercomprising: detecting the IEEE 802 compliant wireless network; andcommunicating with the IEEE 802 compliant wireless network in responseto detecting the IEEE 802 compliant wireless network.
 17. The method ofclaim 16, further comprising: releasing any of the assigned physicallayer channels associated with the first wireless network.
 18. Themethod of claim 16, wherein detecting the IEEE 802 compliant wirelessnetwork comprises receiving a beacon frame or a probe response framefrom the IEEE 802 compliant wireless network.
 19. The method of claim11, wherein at least one of the physical layer channels is a datachannel.
 20. The method of claim 12, wherein the first wireless networkis a code division multiple access (CDMA) wireless network and thesecond wireless network is an IEEE 802.11x compliant wireless network.